A projection-type display device (projector) configuration is known that uses a color separation wheel that rotates at high speed to sequentially separate white light that is emitted from a light source into light of the three primary colors of red, green, and blue and that sequentially light-modulates the colored light that is separated in accordance with a picture signal to form a color picture. The color separation wheel is also referred to as a “color wheel”. A component such as a liquid crystal panel or DMD (Digital Micro-Mirror Device (registered trademark)) is used for the image-forming element.
A projection-type display device of the prior art that uses this type of color separation wheel is disclosed in, for example, Patent Document 1 (JP 2005-300647 A). In Patent Document 1, a method is described for synchronizing the light modulation of the light of each color by an image-forming element with the color separation realized by the color separation wheel.
Among projection-type display devices that use the above-described color separation wheel, most are conventionally of a configuration that uses, for example, a high-luminance discharge lamp as the light source. However, in recent years, projection-type display devices are being developed that use a semiconductor light-emitting element such as a laser diode or LED (light-emitting diode) as the light source for the purpose of obtaining lower power consumption and longer service life of the light source.
For example, Patent Document 2 (WO 2012/127554 A1) discloses a projection-type display device that uses a laser diode that emits laser light of the blue wavelength band as a light source and that irradiates the laser light upon a phosphor to generate light of the red wavelength band and green wavelength band.
The projection-type display device disclosed in Patent Document 2 includes a light emitting wheel that is provided with a red region in which is formed a phosphor that, when excited by laser light of the blue wavelength band, emits light of the red wavelength band, a green region in which is formed a phosphor that, when excited by laser light of the blue wavelength band, emits light of the green wavelength band, and a blue region in which a mirror is formed that reflects the light (laser light) of the blue wavelength band; and when laser light of the blue wavelength band is irradiated upon the light-emitting wheel that is rotating at high speed, sequentially supplies light of the blue wavelength band, red wavelength band, and green wavelength band. A color picture is then formed the sequential light modulation of the light of each color emitted from the light-emitting wheel in accordance with a picture signal.
In a configuration that uses the above-described phosphors to generate light of the red wavelength band and green wavelength band, the light emission efficiency may differ according to the phosphor. For example, it is known that when light of the green wavelength band and red wavelength band are generated from light of the blue wavelength band, the light emission efficiency of the phosphor that emits light of the red wavelength band is lower than that of the phosphor that emits light of the green wavelength band. As a result, methods are being investigated that, instead of using different phosphors to cause light emission of light of the green wavelength band and red wavelength band, cause light of the yellow wavelength band that includes light of the red wavelength band and green wavelength band to be emitted by a phosphor and then use a color filter to color-separate light of the red wavelength band and light of the green wavelength band from the light of the yellow wavelength band. In this case, a color separation wheel should be used to sequentially separate light of the red wavelength band and light of the green wavelength band from light of the yellow wavelength band that was generated by the light-emitting wheel.
If light of the yellow wavelength band is produced in this way and light of the red wavelength band and green wavelength band are separated from the light of the yellow wavelength band, the difference in the brightness of the light of each color that arises from the characteristics of the phosphor can be reduced. Further, if light of the yellow wavelength band is also used in picture display, the brightness of the projected picture can be improved, and the yellow color development in the projected picture (color picture) can also be improved. In the following explanation, the output of light by the light-emitting wheel that has been excited by the light emitted by the light source as well as the output of light due to the transmission or reflection of light emitted by the light source are also referred to as “light output by the light-emitting wheel.
However, in a configuration that uses a light-emitting wheel and a color separation wheel, a method has not been established to adjust the rotation timing of the color separation wheel and light-emitting wheel that rotate at high speed with respect to the timing of the light modulation by an image-forming element.